Ocular smooth muscle is found in the iris and ciliary body of mammals; its function is to automatically change the size of the pupil and the shape of the lens, respectively. The muscles of the ciliary body may also be involved in aqueous humor and mucopolysaccharide secretion. We propose to study the contractile apparatus of each tissue obtained from chicken, rabbit and calf, to determine and compare properties of isolated myofibrils with those of skeletal muscle to learn how the ATPase activity is controlled. Particular emphasis will be placed on studies with purified ocular tropomyosin due to its known tissue-determined properties, and its effect on ATPase activity and Ca2 ion control in other muscles. Electrophoretic and ATPase techniques will be used for protein identification and activity studies. Circular dichroism and fluorescence techniques will be used to study ocular tropomyosin structure.